The present invention broadly relates to composite bearing materials which are comprised of a hard metal backing strip, such as steel, having a bearing lining composed of leaded bronze tenaciously bonded to at least one face surface thereof. Such composite bearing materials are eminently suitable and in widespread use for the fabrication of various bearing components for use in internal combustion engines, vehicle suspensions, transmission assemblies or the like.
Composite bearing materials of the foregoing general type have been produced by processes such as disclosed in U.S. Pat. No. 2,986,464 granted May 30, 1961 to Lewis et al and U.S. Pat. No. 4,002,472 granted Jan. 11, 1977 to LeBrasse et al which are also assigned to the assignee of the present invention. The teachings of the two aforementioned United States patents, to the extent that they are relevant to the present invention, are incorporated herein by reference.
While the processes disclosed and the resultant composite bearing material produced in accordance with the processes described in the aforementioned United States patents are eminently suitable for producing high quality composite bearing materials for the fabrication of various bearing components, less than optimum physical properties of the bearing lining and performance of the bearing components produced therefrom have been obtained due to the presence of relatively large-sized lead particles in the bearing lining. Attempts to overcome this problem by the direct casting of a molten leaded-bronze bearing alloy directly on a steel backing strip has been unsuccessful in overcoming this problem.
The present invention provides for an improved process and an improved composite bearing material produced thereby employing powder metallurgical techniques whereby a satisfactory tenacious bond is obtained between the bearing lining and the steel backing strip employing sintering conditions including time and temperature which inhibit the formation of large-sized lead particles thereby achieving a unique leaded-bronze lining characterized by an extremely fine-sized lead distribution dispersed uniformly throughout the bearing lining matrix.